Manufacture of steel.



UNITED STATES PATENT OFFICE.

HERBERT H. WEAVER, OF UPPER YODER TOWVNSHIP, AND GEORGE E. THACKRAY, OFWVESTMONT BOROUGH, PENNSYLVANIA. I

MANUFACTURE OF STEEL.

Specification of Letters Patent.

Patented Dec. 4, 1906.

Application filed June 18, 1906. Serial No. 322,311.

T0 at whom it may concern/.-

Be it known that we, HERBERT H. WEA- VER, residing in Upper Yodertownship, and GEORGE E. THAOKRAY, residing in the borough of Westmont,in the county of Cambria and State of Pennsylvania, citizens of theUnited States, have invented certain new and useful Improvements in theManufacture of Steel; and we do hereby declare the following to be afull, clear, and exact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

For the manufacture of steel by the Bessemer or pneumatic processesmolten pig-iron is used, and in order to produce the best results thecomposition of this with respect to the contained metalloids should bewithin reasonable limits of variations, and the tendency of the presenttime is to require steel for rails and similar articles with less phosphorus than the previously customary content of one-tenth of one percent, and to best adapt the material for good rolling and use the steelshould also be low in sulfur.

To produce pig-iron that will make steel containing less than one-tenthof one per cent. of phosphorus requires iron ores of preferably highcontents in ironsay from fifty to sixty per cent. of metallic ironandwith phosphorus correspondingly about .035 to .045 per cent. in the ore.As practically none of the phosphorus of the ore is eliminated in theblast-furnace and as the pigiron will also absorb in the process ofsmelting a certain amount of phosphorus from the limestone or other fluxand from the coke or fuel, very low percentages of phosphorus have beenheretofore required in the ores in order to produce the results desired.

Although many millions of tons of ores are mined and used every year inthe United States, it is becoming more difficult to obtain what areknown as Bessemer oresthat is, those which will produce pig-iron thatwill produce steel by the ordinary Bessemer or pneumatic process withphosphorus below one-tenth of one per cent.-but our improved processenables us to use non-Bessemer ores or to improve the quality of steelmade from Bessemer ores. It is also necessary to limit the sulfurcontent of the steel to aid in rolling the same to smooth surface andfor other able character.

reasons, and as little or none of this element is eliminated in theBessemer process this again requires that the pig-iron shall contain acomparatively small percentage of this constituent. Further than this,it is well known that in the operation of a blast furnace varyingconditions of the furnace itself, the atmosphere, and, notwithstandingall the care displayed, the variations in the quality of the ores,fluxes, and fuels will result in making pig-iron of varying compositionwith respect to its contained metalloids, and particularly with regardto the silicon and sulfur contents. In the conduct of the Bessemerprocess it is also necessary that the silicon content shall be kept aslow and uniform as possible within the requirements in order to avoidloss in slag, &c., and to maintain the regularity of the operation, forthe reasons that too much silicon will make a hot heat and too littlewill not roduce enough heat to render the blow uid and homogeneous.

IVith a knowledge of these difficulties we have devised a process forimproving the manufacture of steel, and particularly that made by theacid Bessemer or pneumatic process, which consists, essentially, oftaking comparatively irregular metal from a blastfurnace or a series ofblast-furnaces and introducing it into a large receiver capable ofcontaining approximately one or more hundred tons of molten metal, thisreceiver being either with or without extraneous source of heat,dependent upon the condition desired. In other words, this receiver maybe a large semioylindrical, rectangular, or other shaped vessel ofsuitable size, preferably lined with fire-brick and provided with acover, an opening at one side or the top thereof for the introduction ofmolten pig-iron, a spout arranged at asuitable level for withdrawingmetal therefrom, and means for .tilting or otherwise discharging themolten metal from the receiver as required. If the operation performedtherein is speedy and continuous,

this receiver may workvery well without the aid of any extra heat fromgas, oil, coal, or other fuel; but in order to provide for stoppage orcontingencies and to keep the slag or metal liquid we may furnish thereceiver with heating apparatus of any suit In addition to the receiverwe employ an open-hearth refining-furnace, preferably gasfired, whichmay either have a stationary, revolving, or tipping hearth, as may befound expedient or necessary, one of the prime conditions of thisrefining-furnace being that it shall be provided with a basic lining ofcharacter such as to aid in eliminating phosphorus, sulfur, and siliconfrom molten pig- 1ron introduced therein, and the lining of thisrefining-furnace may be either of lime, dolomite, magnesite, iron ore,iron oxids, or similar materials fused and fritted in place or'previously baked and set in position as may be best. In addition to thisapparatus we use the ordinary blast-furnace and Bessemer converterandthe necessary auxiliaries to the conduct of a process of thischaracter.

In operating our refining-furnace the largest portion or almost all ofthe silicon will be eliminated from the metal, and under best conditionswe can also eliminate from eighty to almost one hundred .per cent. ofthe phosphorus and at the same time a reasonable portion-of the sulfur.In doing this the basic lining of the refining-furnace may be sufficientto accomplish the purifying, or we may use basic additions therein, suchas limestone, lime, dolomite, iron ores, 800. During or prior to thetransfer of the refined metal from the refining-furnace to the receiverwe preferably remove the slag therefrom by decanting, skimming, allowingit to separate by a dam, by overflowing a ladle or other vessel, or inany other way that may be convenient or expedient. The slag from therefiningfurnace is thus prevented from going into the receiver with therefined metal, the purpose of this being to obviate the possibility ofthe impurities, particularly the phosphorus, from being transmitted fromthe slag to the refined or to the mixed metal.

Having thus briefly described the general nature of the process and thepreferred apparatus for conducting same, we will now briefly describethe process itself.

Molten pig-iron from one or more blastfurnaces is introduced into thereceiver before mentioned, and by means of diffusion or agitation, orboth, therein this pig-iron becomes much more uniform in itsnon-metallic constituentssuch as silicon, sulfur, phosphorus, &c.thanthe successive portions which have been introduced. While this is beingdone the refining-furnace is supplied with pig-iron either the same asthat placed in the receiver or it may be either higher or lower in itsnon-metallic constituents. Basic additions, if necessary, may be made tothe charge in the refining-furnace. After the elimination of a largepart of the silicon, most of the phosphorus, and a considerable portionofthe sulfur-in the refining-furnace the purified metal therefrom isseparated from its slag and said purified metal is charged into thereceiver aforesaid, whereupon the blastfurnace metal is diluted with thepurer refined metal, the silicon, phos horns, and sulfur of theresultant mixture eing materially lower than that of the blast-furnacemetal alone.

In charging the receiver with blast-furnace metal or refined metal wemay either fill or partially fill the receiver with a proper admixtureof these two metals in order to pro-- duce the composition desired andthen withdraw from it successive portions sufiicient for a Bessemer blowuntil the receiver is emptied, or we may introduce blast-furnace metaland refined metal therein more or less continuously, keeping at alltimes a quantity of metal in the receiver and withdrawing the requiredportions for a Bessemer blow therefrom at intervals as desired. Bycarefully regulating the quantities and proportions of the refined metaland blast-furnace metal, with due respect to their impurities ornonmetallic constituents, we can produce a mixed iron having asubstantially or approximately uniform content of silicon and lowercontent of phosphorus and sulfur than in the average of blast-furnacemetal.

Another and particular advantage of our process is that it enables us touse blast-furnace metal for charging direct into the receiver, ifnecessary, which contains a higher percentage of silicon than iscustomary or ordinarily necessary in Bessemer practice.

The manufacture of comparatively high silicon iron in a blast-furnace isan easier and more economical process than to attempt to makelow-silicon iron, for the reason that as the silicon decreases in theblast-furnace iron the sulfur correspondingly increases, due to therequired low temperature in smelting and other causes. On account of thefact that our refining-furnace producesa refined iron which is both lowin silicon and other metalloids, this enables us to use highersiliconsin the blast-furnace metals charged into the receiver, the resultantmixture being what is desired and proper. This process includes,therefore, the mixing of irregular blast-furnace metals to render themuniform or with unabrupt changes in their composition from time to time,and in addition to that the lowering of the silicon, sulfur, andphosphorus by the further admixture of refined metal from therefining-furnace aforesaid. We are thus enabled to produce asubstantially uniform metal of best quality for use in the Bessemerconverter which will produce better and more regular results thanheretofore accomplished and furnish a steel with lower phosphorus,sulfur, 850., than could be had by using the blast-furnace metal,either'direct or from a receiver.

Although for the purposes of explanation certain figures, sizes,quantities, and'analyses are herein stated, we of course do not limitourselves to these figures, as they are merely given as examples inelucldation of the objects and purposes of our invention, nor doweconfine ourselves to any specific appa ratus in carrying out the same.

Having thus described our invention, what we claim, and desire to secureto Letters Patent, is-v 1. The process of making steel which consists ofplacing successive portions of molten iron from one or more furnacesinto a receiver, then introducing refined metal from a basicrefining-furnace therein, said refined metal containing less metalloidsthan the furnace metal, allowing the various portions to diffuse andbecome more uniform in their composition and then bessemerizing, in anacid-lined converter, the resultant metal.

2. The process of making steel which consists of introducing into areceiver successive portions of molten iron from one or more furnaces,which portions are of varying composition, then purifying a portion ofsomewhat similar metal in a refining-furnace and there removingconsiderable percentages of the metalloids, including silicon, sulfur,phosphorus, &c., therefrom, then adding said refined metal to the metalin the receiver and making a substantially uniform mixture prior tofurther treatment in an acid-lined Bessemer converter.

3. The process of making steel which consists of introducing in areceiver successive portions of molten iron from one ormore fur naces,which portions are of varying composition, purifying a portion ofsomewhat similar metal in a basic refining-furnace and there removingconsiderable percentages of its contained metalloids, separating therefined metal from the slag produced in the purifying operation,introducing the refined metal into the receiver and making asubstantially uniform mixture prior to treatment in an acidlinedBessemer converter.

4. The steps prior to the bessemerizing of molten iron in an acid-linedconverter which consists of introducing a number or portions of molteniron from one of more furnaces into a receiver, which portions are ofvarying composition with regard to their contained metalloids, purifyingportions of molten pigiron in a refining-furnace and there removingconsiderable percentages of silicon, sulfur,

phosphorus, &c., therefrom, introducin said refined metal into thereceiver aforesai and mixing or diffusing the same with the combinedportions of the furnace metal and then withdrawing portions of theresultant metal for bessemerizing as aforesaid, maintaining during theoperations a considerable quantity of mixed metals in the receiver.

5. The steps prior to the bessemerizing of molten iron in an acid-linedconverter which consists of introducing a number of portions of molteniron from one or more furnaces into a receiver, which portions are ofvarying composition with regard to their contained metalloids, purifyingportions of molten pigiron in a basic refining-furnace and thereremoving considerable percentages of silicon, sulfur, phosphorus, &c.,therefrom, introducing said refined metal into the receiver aforesaidand mixing or diffusing the same with the combined portions of thefurnace metal and then withdrawing portions of the resultant metal forbessemerizing as aforesaid.

6. The process of making a mixture of various portions of molten irondirect from the blast-furnace, which are of varying compositions asregards their non-metallic constituents, introducing therein refinediron which has been purified in a basic lined refiningfurnace, removingthe slag from said refined metal before mixing it with the blastfurnacemetal and then making Bessemer steel in an acid-lined converter from theresultant mixture.

7. The process of making steel which consists of introducing into areceiver various portions of metal direct from a blast-furnace whichportions are of varying composition, mixing the metal in said receiverwith refined molten metal which has been purified in a basic-linedopen-hearth furnace and the slag removed therefrom and then making saidmixture into Bessemer steel in an acid-lined converter.

In testimony whereof we hereto affix our signatures in the presence oftwo witnesses.

HERBERT H. WEAVER. GEORGE E. THAOKRAY.

WVitnesses:

E. M. Lonosnonn, A. E. WEIMER.

